CVE-2026-4408: Red Hat Enterprise Linux

Critical severity, CVSS 9.8. EPSS: 1.8% chance of exploitation in the next 30 days.

A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper escaping of shell meta-characters. This vulnerability allows an attacker to achieve remote command execution on the affected system. This issue primarily affects non-standard configurations where the "check password script" is used with %u and the samba-dcerpcd service is started as a system service.

Affected products

• Red Hat Enterprise Linux: version 6.0 only; version 7.0 only; version 9.0 only
• Red Hat Openshift Container Platform: version 4.0 only
• Samba Samba: from 4.1.0, before 4.21.0 (fixed in 4.21.0)

Published 2026-05-28. Last modified 2026-10-08.